Sophisticated and Strategic

Mission-critical facilities such as data and telecommunications
centers must maintain operations without interruption. Mission
continuity is ensured for facilities through the use of redundant
power supplies and mechanical systems and cuttingedge
fire protection systems.

Fire in these facilities obviously can threaten the business and human life. Key
to defending against a catastrophe is a sophisticated fire protection system that
integrates seamlessly with the entire environment.

Fire protection for mission-critical facilities can be complex and daunting. System
designs should be based on a total fire protection approach in which three
conditions are met: identifying the presence of a fire, communicating the existence
of that fire to the occupants and proper authorities, and containing and extinguishing
the fire, if possible. Being familiar with all technologies associated with
fire detection, alarming and suppression is important to developing a sound fire
protection solution.

Fire Detection Strategies

There are many ways of detecting and suppressing fires, but only a few should be
used for mission-critical applications. For example, the main goal of the fire protection
system in a data center is to get the fire under control without disrupting
the flow of business or threatening occupants.

Spot Detection

For the purposes of protecting a mission-critical facility, addressable early-warning
smoke detectors and heat detectors can be an option. Because the airflows
are rapid in an area such as a data center, it is important to realize the differences
between types of detectors.

Ionization smoke detectors are quicker at detecting flaming fires, such as those
commonly found in chemical storage areas, rather than slow, smoldering fires that
most typically occur in data centers and telecom equipment spaces. Ionization
sensors almost immediately recognize fires characterized by combustion particles from 0.01 to 0.3 microns. However, ionization
sensors offer limited or slower
capabilities when installed in areas with
high airflow, which is often the case in
mission-critical environments.

Photoelectric smoke detectors, however,
quickly respond to smoldering
fires characterized by combustion particles
from 0.3 to 10.0 microns, making
these detectors more appropriate for
most mission-critical settings.

One solution for detecting a broad
range of fires quickly would be a multicriteria
detector that uses photoelectric
particulate detection in tandem with
sensors that detect other products of
combustion, such as carbon monoxide
(CO) and light (infrared). Together,
these signals are cross-referenced by an
onboard microprocessor that uses algorithms
to “process out” false alarms
while enhancing the response time to
real fires.

Another solution is to use intelligent
high-sensitivity detectors, which
are very similar to standard detectors
except that they employ a more highly
advanced detection method.

High-sensitivity spot detection typically
employs a focused laser-based
source to achieve sensitivities that are
100 times more sensitive than standard
addressable or conventional infraredbased
photoelectric smoke detectors.
They are designed to respond to incipient
fire conditions as low as 0.02 percent
per foot obscuration to provide
valuable time for staff to investigate the
affected area and take appropriate action
to mitigate risk.

These detectors are addressable and
able to send information to the central
control station, thereby pinpointing the
exact location of the smoke. Some can
automatically compensate for changes
in the environment, such as humidity
and dirt buildup. They also can be programmed
to be more sensitive during
certain times of the day. For instance,
when workers leave the area, sensitivity
will increase.

High-sensitivity detectors are commonly
placed below raised floors, on
ceilings and above drop-down ceilings,
as well as in air-handling ducts to detect
possible fires within the HVAC system.

Aspirating Smoke Detection

Many air-sampling smoke detectors
also can provide high-sensitivity detection.
Some systems can be up to 1,000
times more sensitive than a standard
photoelectric or ionization smoke detector
and are capable of detecting byproducts
of combustion in concentrations
as low as 0.00046 percent per foot
obscuration. This type of detection
provides advanced notification so facility
managers or other appropriate staff
can intervene and take action before a
combustion event becomes disastrous.

An aspiration system works by
drawing in smoke through a network
of piping via the aspirator (fan). The
air sample is then passed through a
filter and into the sensing chamber of
the detector. Using advanced sensing
technology, the detector analyzes the
air sample and sends a signal of airborne
smoke intensity to a remote or
integrated display module and a fire detection
panel, when necessary, to raise
an alarm.

These detectors communicate information
to a fire alarm control panel,
a software management system or a
building management system through
relays or another interface. With some
systems, email updates can be sent
to appropriate staff to communicate
alarm levels, urgent or minor faults or
other status conditions via relays.
The multiple warning levels of this
system can trigger different responses
at different stages of a fire, from controlling
air conditioning to suppression
release. To accommodate specific codes
or environments, alarm relays can be
set with 0- to 60-second delays.

Fire Suppression Systems

Although smoke detectors primarily
alert of a fire condition, in a missioncritical
facility they may also be used to
control the release of fire suppression
systems. Should a fire occur, suppression
systems are the next line of protection
and can quickly extinguish the fire
with minimal or no effect on the operation.
It is important to consider the
suppression system to be used.

Sprinkler Systems

Sprinkler systems, which are designed
specifically for protecting the structure
of the building, can be installed in four
different configurations: wet-pipe, drypipe,
deluge and pre-action. The wetpipe
system consists of a piping system
connected to a water source and filled
with water so that water discharges immediately
from sprinklers activated by
a fire. In general, wet-pipe sprinklers
are not recommended for mission-critical
facilities; however, depending on
local fire codes, they may be required.

A dry-pipe system is typically used
in areas subject to freezing and consists
of piping connected to a water source
and filled with air pressure supplied by
a compressor. When a sprinkler is activated,
the air is expelled first, allowing
a special check valve, called a dry-pipe
valve, to operate. This allows water to
flow into the piping and out any open
sprinklers. This, too, is not ideal for
mission-critical facilities.

A pre-action system is more common
in a mission-critical facility. “A
pre-action sprinkler system is one effective
alternative because of its dualaction
criteria,” said Ramzi Namek,
director of engineering for Total Site
Solutions, Columbia, Md. “The pipe
remains dry until the fire detection system
activates a control valve (located
outside the data center to avoid damage
from leaks), filling it with water.”

It consists of closed-type sprinkler
heads connected to a series of piping
arrangements. The system has a preaction
valve that prevents the pipes from
filling with water during normal times.
This valve is held closed electrically by
activation of the detection system (fire
detectors) being released only when an
electrical signal is sent to the releasing
solenoid valve. Upon receipt of the signal,
which could be from any of the sensors
attached to the system, an electrical
mechanism opens the pre-action valve,
and the pipelines fill with water under
pressure. The system at that point functions
as a standard wet-pipe system. The
water tanks are located away from the
area but are readily accessible.

“Another important design consideration
to plan for is space for suppressionagent
tanks. Some suppression agents are
stored in gas form; others are stored as a
liquid, which can impact the number and
size of tanks required,” explains Namek.

Clean-agent Suppression

In addition to sprinkler systems, cleanagent
suppression systems can extinguish
fires in their incipient stage, well
before enough heat builds in a room to
activate a sprinkler system. When activated,
these waterless flame-suppression
systems discharge as a gas. The
gas reaches all areas of the protected
facility and leaves no residue to damage
sensitive equipment or require costly
cleanup. Clean agents suppress fires by
many methods, including depleting the
area of oxygen, interrupting the chemical
reactions occurring during combustion,
and absorbing heat.

Clean-agent suppression systems,
protecting both the areas underneath
and above the raised floor, are the most
common method of fire protection
for Class C electrical hazards. “Raised
floors bring up some important issues
with regard to fire protection in mission-
critical facilities,” said Fournier.
Spaces beneath raised floors often experience
many air changes per hour, which
presents a difficult detection design.

“Because raised floors create a completely
separate plenum and pose as
much of a fire hazard as the numerous
pieces of computer equipment situated
on the raised floors,” Fournier said, “they
must be protected with the same level of
fire protection as the space above.”

These clean-agent suppression systems,
when controlled by an interface
with a high-sensitivity smoke detection
system, suppress fires without damaging
IT equipment and allow staff to get
the facility up and running faster.

Regardless of which detectors or
systems are used in the fire and life
safety design in a mission-critical facility,
all must be networked into one
central location. Whether that is a
series of panels or a control center,
there will be a vast amount of equipment
used—hundreds and maybe
thousands of devices, depending upon
the size of the facility. Programming is
the key to how well all the pieces come
together. The outcome for a fire and
life safety system within a missioncritical
system remains to minimize or
prevent a fire event in order to maintain
constant operation and protect
occupants.

This article originally appeared in the March 2012 issue of Security Today.